Compactness is essential for many electronic devices and sensors. Carbon nanotubes have obvious advantages for compact devices, not least because of their small diameters. Now, electrical engineers at Cornell University in the US and Namseoul University in South Korea have shown that it is possible to make structures in which a nanotube transistor shares a gate electrode with a silicon transistor. At the Fall Meeting of the Materials Research Society in Boston last month, Hao Lin of Cornell described how such structures had been used to make a logic device known as an inverter and a prototype chemical sensor1.

Using fabrication techniques that are compatible with silicon technology, the team used both polysilicon and tungsten as gates. The oxide layers in the devices were between 8 and 10 nm thick. Lin and co-workers made the inverter by placing a p-type carbon nanotube field-effect transistor directly on top of an n-type silicon transistor, both of which were controlled by a single polysilicon gate in between them.

The team's approach offers the possibility of combining the excellent electronic properties and sensing potential of nanotubes with established silicon electronics and its highly developed infrastructure.